The invention relates generally to computed tomography (CT) imaging, and more particularly to an apparatus and method for computing volumetric perfusion from temporal reconstructions of tissue attenuation characteristics using digital area detector technology.
As will be appreciated by one skilled in the art, tissue perfusion may be defined as the passage of blood through a volume under consideration. In more specific terms, tissue perfusion may be defined as the flow of blood per unit volume of tissue. Perfusion parameters may include regional blood volume, regional mean transit time, regional blood flow, permeability surface area, and time of arrival. Due to the low contrast of distributed blood volumes in tissues and/or organs, signal-to-noise ratio, dynamic range and frequency resolution in the X-ray detection systems are important factors in systems that perform perfusion imaging. Additionally, another critical factor to consider when computing tissue perfusion is object motion during imaging, which may obscure the low contrast signal.
CT perfusion algorithms may continuously acquire projection data from limited axial coverage of the patient to adequately measure the contrast dynamics, such as uptake and washout of contrast enhancing medium in the tissue or organ being imaged. Multi-row detector technology facilitates the simultaneous acquisition of multiple slices (for example, 16 slices in some systems) of projection data to be acquired, reconstructed, and processed for perfusion evaluation. Such systems may provide adequate temporal sampling of the contrast dynamics of the tissue in spatially stationary organs; however, these systems do not provide the axial coverage to image the whole organ.
CT imaging techniques may present certain challenges when imaging dynamic internal structures or organs, such as the heart. For example, in cardiac imaging, the motion of the heart causes inconsistencies in the projection data, which, after reconstruction, may result in various motion-related image artifacts such as blurring, streaking, or discontinuities. In particular, artifacts may occur during cardiac imaging when projections that are not acquired at the same point in the cardiac cycle, i.e., the same phase, are used to reconstruct the image or images that comprise the volume.
It may therefore be desirable to develop techniques to advantageously enhance the temporal resolution in reconstructed data representative of spatially dynamic and/or temporally dynamic objects, such as for a heart and/or a heart perfused with contrast agent respectively.